The Fabrication of Oleophobic Coating and Its Application in Particulates Filtration
Round 1
Reviewer 1 Report
Dear Sir,
The manuscript presents an ingenious solution to the problem of air purification from potentially harmful oily aerosols, by improving an existing procedure. Moreover, among the advantages of the proposed method would be the potential recovery of the filtered oil (which would be otherwise disposed along the saturated filter) and its subsequent use in the production of other products (e.g. biodiesel and such) and a longer shelve life for the filters (which means a smaller number of filters used per year).
The manuscript is well-written and the study correctly conducted. I do not have objections, but a few suggestions:
1) could the authors add a SEM image of oil-adhered of uncoated PVDF for comparison in Fig. 1?
2) when the authors mentioned that oleophobic membranes were used in the treatment of oily wasterwaters, please use more pertaining references, specifically papers in which PVDF-type membranes were used (e.g. https://doi.org/10.1016/j.memsci.2014.04.038; https://doi.org/10.1016/j.jece.2022.107258; https://doi.org/10.1016/j.seppur.2017.10.027; https://doi.org/10.22146/ijc.43314 etc.), eventually mentioning in the text the chemical nature of the oleophobic coating.
3) what would be the life span of a coated filter compared to the uncoated one?
4) I presume that after a certain number of working hours, even the coated filter must be replaced. What would happen to the “spent” filter? Is it to be disposed of or is it possible to make a “re-coating” and reuse the filter?
5) since the most exposed to oily droplets are the cooks and personel working inside kitchens, can the methodology be applied to the development of individual face-masks or hair-protections?
Author Response
Replies to Reviewer 1
We appreciate the reviewer for these constructive suggestions. The detailed responses are listed below:
- Could the authors add a SEM image of oil-adhered of uncoated PVDF for comparison in Fig. 1?
Author reply: The oil-adhered morphologies of uncoated PVDF is listed as below. According to the SEM image, the adhered oil particles or oil film accumulated on the uncoated PVDF fibers, which will sharply increase the pressure drop of airflow.
- When the authors mentioned that oleophobic membranes were used in the treatment of oily wasterwaters, please use more pertaining references, specifically papers in which PVDF-type membranes were used (e.g. https://doi.org/10.1016/j.memsci.2014.04.038;https://doi.org/10.1016/j.jece.2022.107258; https://doi.org/10.1016/j.seppur.2017.10.027; https://doi.org/10.22146/ijc.43314 etc.), eventually mentioning in the text the chemical nature of the oleophobic coating.
Author reply: The above-mentioned references and the chemical nature of the oleophobic coating are complemented in the main text, which will make the text more scientific and the reference more related.
- What would be the life span of a coated filter compared to the uncoated one?
Author reply: Compared to the uncoated, the coated filter has a far longer life span than the uncoated one, since the oil particles could not easily adhere on the oleophobic fibers. On the contrary, the lipophilicity of uncoated fibers induces the adhesion of oil particles and sharply increase the airflow pressure drop, which will decrease the life span immediately.
- I presume that after a certain number of working hours, even the coated filter must be replaced. What would happen to the “spent” filter? Is it to be disposed of or is it possible to make a “re-coating” and reuse the filter?
Author reply: It’s definitely true that the coated filter must be replaced after certain numbers of cleaning processes. Until now, almost all of the ‘spent’ filters including commonly used filters and masks are discarded randomly without any recovery or reuse, which will greatly aggregate the environmental pollution. Actually, recoating is difficult since the fibers’ surfaces are covered by the oil films. However, we will use degradable polymers to fabricated the filters in our subsequent researches, which will help to relive the secondary pollutions caused by the disposable filters.
- Since the most exposed to oily droplets are the cooks and personal working inside kitchens, can the methodology be applied to the development of individual face-masks or hair-protections?
Author reply: We are sure that the methodology and the fabricated fibers could be applicated in the individual face masks and hair-production when staying inside kitchens, since their filtering fibers are similar. However, when considering the application in face masks, biocompatibility should be carefully considered to meet the requirements of related standards.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The article on the topic "The Fabrication of Oleophobic coating and its application in Particulates Filtration" has novelty and useful practical application of the conducted research. In my opinion, the work can be published, but after the following corrections:
1. Before each reference to the literary sources, a space must be placed. Links [16-20], [28-33] and [35-38] should be removed so that they do not spoil the order of articles, with subsequent links (for example: 16 comes after 21, but it’s correct if first 16... then 17, 18, 19, 20 and 21…).
2. In paragraph 2.3 add the pH of the mixture to be sprayed and in one sentence write the equipment and spraying mode. This information is of some use and your contribution to the general experience of spraying solutions other than paints.
3. In the diagram Fig. 1(a) make the picture of the spray gun more legible, show a blue to dark blue the torch gradient to show that the solution is being sprayed onto the surface of the canvas) and add the caption “spraying SPFO”. Also add captions to the right image of Fig.1(a), for example: dirty air flow, purified or filtered air flow. In the middle image, complement the illustration of the light blue surface by adding SPFO carbon chains, similar to Figure 3(c).
4. Still don't understand why the thickness of PVDF fibers before and after SPFO treatment as shown in fig. 1 SEM (b and c), too different? i.e. their thickness increases with SPFO, but as a result of what, it is not clear… could the SEM images have been taken at different magnifications? Expand the description of the top left spray illustration in Fig. 1… The top roller runs over the web after spraying SPFO, won't it contribute to coarsening the PVDF fibers?
5. The parameters presented in Table 1 (filtration efficiency and airflow resistance) for the modified and original PVDF should be better matched with the conclusions written below. In my opinion, it is now shown that as a result of the SPFO treatment, there was some deterioration in filtration efficiency (99.41% to 94.12%) and airflow resistance (26 Pa to 69 Pa). But at the same time, the procedures presented can introduce the range of these parameters, in which fall as the original and modified PVDF. Also, in Table 1 for oil-accumulated SPFO coated PVDF, the same parameters should be added and a comparative analysis should be carried out similarly to the original PVDF.
6. For SEM in Fig. 4 there is not enough information about how these objects were prepared for microscopy. To better represent differences between different cleaning amount, the SEM contrast should be increased.
7. Something happened with the display of the text on lines 242-243, it should be below the figure caption of Figure 4.
8. In references the literary source [33] do not have doi.
Comments for author File: Comments.docx
Author Response
Replies to Reviewer 2
We appreciate the reviewer for these insightful comments and suggestions. The detailed responses are listed below.
- Before each reference to the literary sources, a space must be placed. Links [16-20], [28-33] and [35-38] should be removed so that they do not spoil the order of articles, with subsequent links (for example: 16 comes after 21, but it’s correct if first 16 ... then 17, 18, 19, 20 and 21…).
Author reply: All of the format mistakes, and we have also checked the whole text thoroughly to avoid similar mistakes.
- In paragraph 2.3 add the pH of the mixture to be sprayed and in one sentence write the equipment and spraying mode. This information is of some use and your contribution to the general experience of spraying solutions other than paints.
Author reply: pH of the solution is 7.0006, which is a neutral environment. The relative parameters including the sparing equipment and spraying mode are illustrated in the main text to clarify the detailed processes of SPFO fabrication.
- In the diagram Fig. 1(a) make the picture of the spray gun more legible, show a blue to dark blue the torch gradient to show that the solution is being sprayed onto the surface of the canvas) and add the caption “spraying SPFO”. Also add captions to the right image of Fig.1(a), for example: dirty air flow, purified or filtered air flow. In the middle image, complement the illustration of the light blue surface by adding SPFO carbon chains, similar to Figure 3(c).
Author reply: The diagram of Fig. 1a is modified in which the spray gun is more legible, and the captions are also illustrated, which makes the figure clearer and easier to understand. The SPFO carbon chains are complemented on the light blue surface.
- Still don't understand why the thickness of PVDF fibers before and after SPFO treatment as shown in fig. 1 SEM (b and c), too different? i.e. their thickness increases with SPFO, but as a result of what, it is not clear… could the SEM images have been taken at different magnifications? Expand the description of the top left spray illustration in Fig. 1… The top roller runs over the web after spraying SPFO, won't it contribute to coarsening the PVDF fibers?
Author reply: Surely the SEM images have been taken at different magnifications, and the fibers’ diameters are actually different. It could be probably attributed to some factors. First, the SPFO coating indeed increased the fibers’ diameter by covering the fibers’ surfaces. Second, the interaction between SPFO solution and fibers will induce the swelling effects, which will apparently increase the fibers thickness. However, another possible reason is that the fabricated PVDF fibers’ diameter is not so uniform, which will partly influence the fiber diameter after coating.
- The parameters presented in Table 1 (filtration efficiency and airflow resistance) for the modified and original PVDF should be better matched with the conclusions written below. In my opinion, it is now shown that as a result of the SPFO treatment, there was some deterioration in filtration efficiency (99.41% to 94.12%) and airflow resistance (26 Pa to 69 Pa). But at the same time, the procedures presented can introduce the range of these parameters, in which fall as the original and modified PVDF. Also, in Table 1 for oil-accumulated SPFO coated PVDF, the same parameters should be added and a comparative analysis should be carried out similarly to the original PVDF.
Author reply: Thanks for your thorough comments. Actually, the filtration efficiency exhibits about 5% decrease probably because the micro-structures of the fibers are slightly disorganized during the coating process. At the same time, the SPFO coating will increase the fibers’ diameters, hence decreasing the porosity, which will obviously increase the airflow resistance. However, compared with the uncoated fibers, the increasing of airflow resistance is reasonable and acceptable. The oil-accumulated SPFO coated PVDF is inserted in Table 1, and the comparative analysis was added in the main text.
- For SEM in Fig. 4 there is not enough information about how these objects were prepared for microscopy. To better represent differences between different cleaning amount, the SEM contrast should be increased.
Author reply: The detailed information about the objects in Fig.4 are added in the main text and figure caption. In order to compare the differences between these objects after cleaning, the SEM images with same scale are captured in figure 4a.
- Something happened with the display of the text on lines 242-243, it should be below the figure caption of Figure 4.
Author reply: We are sorry about the display error, which may be caused by the display screen on Mac and Windows (sometimes it is different). We have checked the whole format style on another compute, if it is still not well displayed, a final pdf version could help.
- In references the literary source [33] do not have doi.
Author reply: The doi of literary source [33] (it is currently ref. [40] because we have complemented some references) is added in the main text, and other references are also checked again to make sure that the doi is listed.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The article is well corrected, but the authors probably just forgot to put spaces before the brackets. I still recommend doing it.
Also, many thanks for the detailed comments on questions 4 and 5. I also have a small comment based on my work experience with PVDF coatings regarding the drying temperature. You can try raising the temperature to 40 °C (max 50 °C), which should be gentle on the polymer material, speed up the drying of the PVDF, preventing it from swelling too much. Then the characteristics of your modified material should improve. In this regard, I also recommend including in the conclusion of the article the phrase that the method of modification with a SPFO solution can be further improved by using a higher drying temperature, the profitability of introducing into production of which may require additional research.
Comments for author File: Comments.docx
